1. Field of the Invention
The present invention relates to a timing signal converter for use in a recording/playback apparatus having a rotary head drum to record or reproduce a time code unsynchronized with the rotation of a rotary head thereof (e.g., a time code in the longitudinal direction of a recording tape) without the necessity of employing a fixed time code recording/playback head.
2. Description of the Prior Art
In a rotary head type recording/playback apparatus, it is necessary to record or reproduce a time code unsynchronized with the rotation of the rotary head.
For example, in a rotary head type digital audio tape recorder (R-DAT), it may be necessary to record a longitudinal time code (LTC) on a tape for use by a video tape recorder (VTR) to facilitate for editing and so forth. In such case, it becomes necessary for a recording/playback section to operate in compliance with a timing signal synchronized with the rotary head, and also for an input/output signal section to operate in compliance with another timing signal such as a longitudinal time code unsynchronized with the rotary head.
For meeting such requirement, a control signal is recorded for controlling the longitudinal time code (LTC) or the motion of a tape, on a track separately from a slant recording track formed by the rotary head. According to the above method, however, it is necessary to provide a fixed head, in addition to the ordinary rotary head, for recording a time code in the longitudinal direction of the tape.
The present applicant proposed an improvement previously as disclosed in Japanese published patent application Ser. No. Sho 63 (1988)29391, wherein the necessity of forming a longitudinal recording track by a fixed head is eliminated by recording a converted time code in a sub-code area of a slant recording format in an R-DAT recording medium.
According to the technique disclosed in Japanese published patent application Ser. No. Sho 63 (1988)-29391, in an exemplary case wherein a 30-Hz time code corresponding to a head rotation rate of 30 r.p.m. in a rotary head type VTR is recorded, it becomes possible to record and reproduce a 30-Hz time code in an R-DAT recording medium where a head is driven at a rate of 100/3 r.p.m. In order to do so the apparatus includes a time code reader, a time code generator, a counter for counting the number of bits, and a latch circuit for latching the counted value, wherein a carry pulse for the counter is generated at a predetermined value and is supplied as a reference synchronizing signal.
However, where the above-described technique is embodied in a practical hardware structure, it is considered desirable, due to the need to combine other related operations, to provide a microprocessor (MPU) for synchronously controlling the time code reader and the time code generator, or to enable the microprocessor to perform both generation and reading of the time code.
In this case, as shown in FIG. 4 representing an exemplary operation time allocation, a microprocessor operation based on a timing signal synchronized with a rotary head can interfere with an operation based on another timing signal unsynchronized with the rotary head. Consequently, it is necessary to interrupt one operation while performing the other operation or to provide a period free from any interruption so as to execute a batch of jobs. As a result of such process, a temporal noncoincidence is induced which eventually results in a timing discrepancy, a partial imcompletion of the job, and partial carry-over thereof to the next cycle. Moreover, it is not easy to prepare a microprocessor program with an interrupt process which includes solutions for the above problems.